Cannabidiol (CBD, C21H30O2, CAS Registry No. 13956-29-1) is an active cannabinoid present in cannabis, a genus of flowering plants that includes Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Other cannabinoids include tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THC-a), cannabinol (CBN), and cannabichromene (CBC).
CBD and THC-a are main components of the marijuana plant. For decades, the CBD content in marijuana plants was very low (below 5%), and all efforts were directed toward increasing the content of psychoactive component of marijuana—THC—for recreational purposes. Recently however, extensive medical research of medicinal attributes of marijuana suggests that CBD is the most important a non-psychoactive component of marijuana that possesses a wide range of therapeutic benefits.
Growers of marijuana developed new strands of the plant with high content of CBD. When subjected to an extraction process the yield of CBD in the concentrated extract (oil, shatters) may approach 70% by weight and higher. The increased CBD concentration made it possible to formulate products consumed as edibles, tinctures capsules, lotions, and creams containing medicinal quantities of CBD. The CBD in such products has been used for serious therapeutic medical treatments such as: reversing alcohol induced brain damage, treating of severe social anxiety, turning off the cancer gene found in metastasis, effectively treating schizophrenia and epilepsy, treating neurogenerative disorders or even slowing down Parkinson's disease and Alzheimer's disease.
Successful use of CBD for medical treatments such as the foregoing depends on the dose of the medicine, reducing side effects, and patient compliance. Orally taken CBD is exposed to the gastric environment and liver, which metabolizes the medicine and thereby lowers its bioavailability. Creams and lotions act for a short time being rubbed off by cloth and washed off.
Transdermal delivery is an alternate route for delivering potent medicines. It circumvents the gastric system, and therefore, the medical substance does not cause liver damage and has increased bioavailability. In particular, children are most susceptible to such damage and may particularly benefit from the transdermal delivery of CBD because transdermal delivery allows for the controlled, sustained delivery of CBD to the body for at least 24 hrs—and possibly for 2-3 days—without damaging young livers.
Transdermal delivery of cannabinoids has been proposed. However, known reservoir-style transdermal devices have used liquid carriers and/or hydrophobic rate-controlling membranes and carriers which have undesirably limited the rate of mass transfer of CBD through the skin. In addition, certain known reservoir-style devices require an additional adhesive coated overlay to hold the device in place on the wearer's skin.
Monolithic transdermal devices (also known as “drug-in-adhesive” devices) for delivering cannabinoids have also been proposed. However, the adhesive used in such known devices has typically limited the rate of mass transfer of CBD to the skin.
Thus, a need has arisen for a transdermal device for delivering CBD.